"Rapid Exchange"-type balloon dilatation catheters are catheters which are capable of advancement into the vascular system of a patient along a preemplaced guidewire for balloon angioplasty or the like, in which the guidewire occupies a lumen of the catheter in only a distal portion thereof. With respect to the catheter proximal portion, the guidewire exits from the internal catheter lumen and extends along the side of the catheter, being typically retained in that position by a guiding catheter in which both the catheter and the guidewire are contained. Examples of catheters of this general type include those disclosed in Horzewski et al. U.S. Pat. No. 4,748,982; Bonzel U.S. Pat. No. 4,762,129; and Yock U.S. Pat. No. 5,040,548.
In the catheters of the above-cited patents, the distal guidewire lumens of the catheters shown have an aperture through which the guidewire can extend, so that in portions of the catheter proximal thereto the guidewire is outside of the catheter, running essentially parallel to it. By this means, the use of a guidewire extension can be avoided when exchanging catheters, providing a more rapid exchange.
A disadvantage of "rapid exchange" type catheter systems having a lateral aperture is that the guidewire cannot be removed and exchanged while the catheter is indwelling in the patient. Furthermore, the reduced length of engagement between the guidewire and catheter can compromise the handling characteristics of the catheter. Likewise, the guidewire lumen of such catheters cannot be flushed with fluids to clear out obstructions and the like, since the patent guidewire lumen is not in fluid communication with the proximal catheter hub.
The conventional, over-the-wire mode of catheter administration lacks these disadvantages, but presents the user a different and substantial disadvantage in that, typically, it becomes necessary to attach a catheter extension wire to the proximal end of the guidewire in order to exchange catheters without moving the guidewire out of position in the patient. However as an advantage of the over-the-wire mode, the guidewire may be quickly and easily removed and replaced without moving the catheter that surrounds it out of position. In the typical "rapid exchange" type of catheter, the guidewire usually cannot be replaced while retaining the catheter in position.
By this invention, a catheter is provided which is capable of use in the normal, over-the-wire mode of surgical use of conventional catheters that lack any side aperture or slit, to achieve the known advantages of that system. However, if it becomes desirable to use the catheter of this invention in the "rapid exchange" mode of operation, to gain those advantages, that can also be accomplished.